This invention relates generally to radio frequency (RF)/microwave/millimeter wave devices, and in particular, to a single-stage, low-pass filter, single-stage, high-pass filter, low-pass filter comprising a plurality of single-stage, low-pass filters, high-pass filter comprising a plurality of single-stage, high-pass filters, and a band-pass filter or other types of filters comprising any combination of one or more single-stage, low-pass filters and one or more single-stage, high-pass filters.
Filters are used extensively for RF/microwave/millimeterwave applications. For example, filters are used to remove higher frequency products from a down-converted signal, to remove lower frequency products from an up-converted signal, to remove harmonics, spurious and other unwanted signals from the output of a local oscillator.
Certain characteristics are generally desirable of filters. For instance, it is generally desirable for filters to have relatively low insertion and return loss within its pass band, yet relatively high rejection and return loss within its reject band. It is also generally desirable to have filters that can be implemented efficiently within a given space. Additionally, it is generally desirable to have filters that can be easily designed and manufactured. For example, it is generally desirable to have filters that can be easily scaled in size for other frequencies.
Such needs and others are met with the various filters described herein in accordance with the invention.
An aspect of the invention relates to a single-stage, low-pass filter. The single-stage, low-pass filter comprises input and output transmission lines, a series transmission line having a first end connected to the input transmission line and a second end connected to the output transmission line, a first meandered transmission line comprising at least two electromagnetically coupled transmission lines and at least one transition transmission line connecting together respective pairs of coupled transmission lines wherein one of the coupled transmission lines includes an end coupled to the input transmission line, and a second meandered transmission line comprising at least two coupled transmission lines and at least one transition transmission line connecting together respective pairs of coupled transmission lines wherein one of the coupled transmission lines is connected to the output transmission line. All of the above transmission lines can be formed on one or more dielectric substrates.
Another aspect of the invention relates to a single-stage, high-pass filter. The single-stage, high-pass filter comprises input and output transmission lines, and a pair of series coupled transmission lines, wherein one of the series coupled transmission lines is coupled to the input transmission line and the other series coupled transmission line is coupled to the output transmission line. The single-stage, high-pass filter further comprises a first meandered transmission line comprising at least two coupled transmission lines and at least one transition transmission line connecting together respective pairs of coupled transmission lines wherein one of the coupled transmission lines is coupled to the input transmission line, and a second meandered transmission line comprising at least two coupled transmission lines and at least one transition transmission line connecting together respective pairs of coupled transmission lines wherein one of the second coupled transmission lines is connected to the output transmission line. All of the above transmission lines can be formed on one or more dielectric substrates.
Other aspects of the invention include a low-pass filter comprising a plurality of single-stage, low-pass filters coupled in series, a high-pass filter comprising a plurality of single-stage, high-pass filters coupled in series, a band-pass filter comprising a combination of one or more single-stage, low-pass filters and one or more single-stage, high-pass filters, and any other types of filters that comprise one or more single-stage, low-pass filters and/or one or more single-stage, high-pass filters. Other aspects, features and techniques of the invention will become apparent to one skilled in the relevant art in view of the following detailed description of the invention.